At school entry, girls are rated by teachers as more competent on measures of social skills than boys. It is less clear if this higher rating is stable or grows over time. To address this question, multiple group curve of factors models investigated gender-specific growth trajectories across seven waves of measurement in a large, longitudinal sample (N = 1024, NICHD SECCYD). Results showed that girls' social skills were consistently rated higher from kindergarten to sixth grade, and the effect size was moderate (latent Cohen's "d" = 0.37 to 0.62). Boys demonstrated greater heterogeneity in social skills at nearly every grade with the gender difference in variability stable after second grade. An examination of gender differences in growth trajectories showed that boys demonstrated a linear decrease over time, whereas girls' social skills did not significantly change over time after accounting for initial level of social skills in kindergarten.